@kellyeung13,
Such discussions been brought up in the past. Perhaps you could visit http://forum.lowyat.net/topic/1071270 and go through to see what most members are saying.

Personally, if Ur going to get a brand new iPhone, I suggest U go for the iPhone 3GS - in fact a couple of forummers here have already switched to the iPhone 3GS (at least 6 and counting). If money is an issue and Ur not really much into gaming on ur iPhone then I guess the 3G might be sufficient [in which case, U can consider purchasing my 2nd hand unit - ok, i better stop advertising before someone "reports" me]

It's hard to comment about the price because Maxis has yet to introduce its pricing on the iPhone 3GS.